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arXiv · 1307.8328

Wigner and Kondo physics in quantum point contacts revealed by scanning gate microscopy

B. Brun·F. Martins·S. Faniel·B. Hackens·G. Bachelier·A. Cavanna·C. Ulysse·A. Ouerghi·U. Gennser·D. Mailly·S. Huant·V. Bayot·M. Sanquer·H. Sellier
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Abstract

Quantum point contacts exhibit mysterious conductance anomalies in addition to well known conductance plateaus at multiples of 2e^2/h. These 0.7 and zero-bias anomalies have been intensively studied, but their microscopic origin in terms of many-body effects is still highly debated. Here we use the charged tip of a scanning gate microscope to tune in situ the electrostatic potential of the point contact. While sweeping the tip distance, we observe repetitive splittings of the zero-bias anomaly, correlated with simultaneous appearances of the 0.7 anomaly. We interpret this behaviour in terms of alternating equilibrium and non-equilibrium Kondo screenings of different spin states localized in the channel. These alternating Kondo effects point towards the presence of a Wigner crystal containing several charges with different parities. Indeed, simulations show that the electron density in the channel is low enough to reach one-dimensional Wigner crystallization over a size controlled by the tip position.

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B. Brun, F. Martins, S. Faniel, B. Hackens, G. Bachelier, A. Cavanna, C. Ulysse, A. Ouerghi, U. Gennser, D. Mailly, S. Huant, V. Bayot, M. Sanquer, H. Sellier. 2013-07-31. Wigner and Kondo physics in quantum point contacts revealed by scanning gate microscopy. https://doi.org/10.1038/ncomms5290

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